Lens barrel incorporating a rotatable optical element

Abstract

A lens barrel includes an imaging optical system including a plurality of lens groups located on an optical axis; an insertable/rotatable optical element which produces a specific photographic effect when rotated on the optical axis; and a drive mechanism including a motor which moves the insertable/rotatable optical element between an inserted position, in which the insertable/rotatable optical element is positioned on the optical axis, and a removed position, in which the insertable/rotatable optical element is removed from the optical axis by forward and reverse rotations of the motor, respectively. The drive mechanism rotates the insertable/rotatable optical element on the optical axis by the forward rotation of the motor when the insertable/rotatable optical element is in the inserted position.

1. A lens barrel comprising:
 an imaging optical system including a plurality of lens groups located on an optical axis; 
 an insertable/rotatable optical element which produces a specific photographic effect when rotated on said optical axis; and 
 a drive mechanism including a motor which moves said insertable/rotatable optical element between an inserted position, in which said insertable/rotatable optical element is positioned on said optical axis, and a removed position, in which said insertable/rotatable optical element is removed from said optical axis by forward and reverse rotations of said motor, respectively, 
 wherein said drive mechanism rotates said insertable/rotatable optical element on said optical axis by said forward rotation of said motor when said insertable/rotatable optical element is in said inserted position. 
 
     
     
       2. The lens barrel according to  claim 1 , wherein said drive mechanism comprises:
 an insertable/retractable frame pivoted about a pivot parallel to said optical axis to be rotatable forward and reverse to move said insertable/rotatable optical element between said inserted position and said removed position; 
 an annular holding frame which holds said insertable/rotatable optical element, and is rotatably supported by said insertable/retractable frame; and 
 a gear train for transmitting a rotational driving force of said motor to said annular holding frame. 
 
     
     
       3. The lens barrel according to  claim 2 , wherein said gear train comprises:
 a sun gear arranged coaxially with said pivot to be rotatable thereon; 
 a planetary gear which meshes with said sun gear, said planetary gear being rotatably supported by said insertable/retractable frame and capable of transmitting a rotation thereof to said annular holding frame; and 
 a drive controller which causes said planetary gear revolve forward and reverse around said sun gear while rotating on an axis of said planetary gear in accordance with forward and reverse rotations of said motor when said insertable/retractable frame rotates forward and reverse to move said insertable/rotatable optical element between said inserted position and said removed position, respectively, and further causes said planetary gear to rotate on said axis thereof without changing a relative position between said planetary gear and said sun gear to thereby rotate said annular holding frame in accordance with said forward rotation of said motor when said insertable/retractable frame is in a position so that said insertable/rotatable optical element is positioned at said inserted position. 
 
     
     
       4. The lens barrel according to  claim 3 , wherein said drive controller comprises:
 a rotation-resistance imposing member which imposes rotational resistance on at least one gear of said gear train; and 
 a rotation limit member which prevents said insertable/retractable frame from further rotating forward to thereby prevent said insertable/rotatable optical element from moving beyond said inserted position when said insertable/rotatable optical element is positioned at said inserted position, 
 wherein, when said rotation limit member does not prevent said insertable/retractable frame from rotating, said rotation-resistance imposing member prevents said planetary gear from rotating about said axis thereof so that said planetary gear revolves around said sun gear in accordance with forward and reverse rotations of said motor, and 
 wherein, when said rotation limit member prevents said insertable/retractable frame from rotating at said inserted position of said insertable/rotatable optical element, said rotation-resistance imposing member allows said planetary gear to rotate about said axis thereof in accordance with said forward rotation of said motor. 
 
     
     
       5. The lens barrel according to  claim 1 , wherein said insertable/rotatable optical element comprises a polarizing filter. 
     
     
       6. The lens barrel according to  claim 1 , wherein said insertable/rotatable optical element is rotated about said optical axis by said drive mechanism when positioned at said inserted position. 
     
     
       7. The lens barrel according to  claim 1 , further comprising a second drive mechanism which positions said plurality of lens groups on said optical axis in a ready-to-photograph state of said lens barrel, removes a part of said plurality of optical elements to a position off said optical axis, and moves said removable part of said plurality of lens groups rearward together with at least a part of the remaining part of said plurality of lens groups, which remain on said optical axis, when said lens barrel is moved from said ready-to-photograph state to a fully-retracted state,
 wherein said drive mechanism moves said insertable/rotatable optical element independently of said removable part of said plurality of lens groups between said inserted position and said removed position in said ready-to-photograph state of said lens barrel, and moves said insertable/rotatable optical element to said removed position and further moves said insertable/rotatable optical element rearward together with said removable part of said plurality of lens groups when said lens barrel changes from said ready-to-photograph state to said fully-retracted state. 
 
     
     
       8. The lens barrel according to  claim 2 , wherein said insertable/retractable frame comprises a front support plate and a rear support plate which are fixed to each other with said annular holding frame and at least a part of said gear train being held between said front support plate and said rear support plate. 
     
     
       9. The lens barrel according to  claim 8 , wherein said annular holding frame comprises a gear which is formed on an outer edge of said annular holding frame to be engaged with a relay gear of said gear train. 
     
     
       10. The lens barrel according to  claim 8 , wherein at least one of said front support plate and said rear support plate comprises a circular flange positioned between said front support plate and said rear support plate, said annular holding frame being fitted on said circular flange to be freely rotatable relative thereto on an axis of said circular flange. 
     
     
       11. The lens barrel according to  claim 8 , wherein at least one of said front support plate and said rear support plate comprises at least one pin on which at least one gear of said gear train is rotatably fitted. 
     
     
       12. A lens barrel comprising:
 a plurality of lens groups arranged on an optical axis; 
 a specific-effect optical element which can be rotated on an axis thereof and can be inserted into and removed from an optical path on said optical axis; and 
 a drive mechanism including a motor which inserts and removes said specific-effect optical element into and from said optical path to be positioned on and off said optical axis by forward and reverse rotations of said motor, respectively, 
 wherein said drive mechanism rotates said specific-effect optical element on said optical axis while holding said specific-effect optical element in said optical path by said forward rotation of said motor when said specific-effect optical element is positioned on said optical axis.